1. Field of the Invention
The present invention relates to an air conditioning system which can utilize stored heat to improve heating capacity.
2. Discussion of the Background
Referring to FIG. 11, there is shown the refrigerant circuit in a conventional air conditioning system which has been disclosed in e.g. Japanese Unexamined Patent Publication no. 273770/1988. In FIG. 11, reference numeral 1 designates a compressor. Reference numeral 2 designates a four way reversing valve. Reference numeral 3 designates an indoor heat exchanger. Reference numeral 4 designates a first pressure reducing device. Reference numeral 5 designates an outdoor heat exchanger. Reference numeral 6 designates a thermal storage heat exchanger. Reference numeral 7 designates a two way low pressure side valve. Reference numeral 8 designates a thermal storage releasing bypass circuit. Reference numeral 9 designates a low side pressure reducing device. Reference numeral 10 designates a thermal storage releasing heat exchanger. Reference numeral 11 designates a thermal storage bypass circuit. Reference numeral 12 designates a two way medium pressure side valve. Reference numeral 13 designates a thermal storage device. Reference numeral 14 designates a thermal storage material. The thermal storage heat exchanger 6 and the thermal storage releasing heat exchanger 10 are immersed in the thermal storage material 14 and is housed in the thermal storage device 13.
The operation of the refrigerant citcuit will be explained. In a heating and thermal storage operation, the two way medium pressure side valve 12 is closed, and the two way low pressure side valve 7 is opened. A gaseous refrigerant which has high temperature under high pressure and has been discharged from the compressor 1 passes through the four way reversing valve 2, and carries out heat exchange with indoor air at the indoor heat exchanger 3 to perform heating. Due to such heat exchange, the refrigerant becomes a liquid refrigerant having normal temperature under high pressure. The liquid refrigerant is depressurized by the first pressure reducing device 4, and stores heat in the thermal storage material 14 at the thermal storage heat exchanger 6. After that, the refrigerant is evaporated at the outdoor heat exchanger 5 to become a gas. The gaseous refrigerant pathes through the four way reversing valve 2 again, and returns to the compressor 1. At that time, the thermal storage material 14 is melted due to such heat storage.
In a defrosting operation, the two way medium pressure side valve 12 is opened, and the two way low pressure side valve 7 is closed. The gaseous refrigerant which has high temperature under high pressure and has been discharged from the compressor 1 passes though the four way reversing valve 2, and carries out heat exchange with the indoor air at the indoor heat exchanger 3 to partly perform heating. Due to such heat exchanging, the refrigerant becomes a two phase refrigerant having high temperature under high pressure. The two phase refrigerant is depressurized by the first pressure reducing device 4, passes through the thermal storage bypass circuit 11, and reaches the outdoor heat exchanger 5. At the outdoor heat exchanger 5, the refrigerant melts frost which has deposited on the surface of the outdoor heat exchanger 5. Due to such defrosting, the refrigerant becomes a liquid refrigerant having low temperature under medium pressure. The liquid refrigerant pathes through the thermal storage releasing bypass circuit 8, is depressurized by the low side pressure reducing device 9, and withdraws the stored heat from the thermal storage material 14 at the thermal storage releasing heat exchanger 10 to be evaporated and gasified. The refrigerant thus gasified returns to the compressor 1. At that time, the thermal storage material 14 is solidified by passing the stored heat to the refrigerant. This arrangement aims at enabling heating even during defrosting, and preventing an indoor temperature from lowering during defrosting.
In a heating kickoff operation, the two way medium pressure side valve 12 is opened, and the two way low pressure side valve 7 is closed like the heating and defrosting operation. The refrigerant which has high temperature under high pressure and has been discharged from the compressor 1 passes through the four way reversing valve 2, and carries out heat exchange with the indoor air at the indoor heat exchanger 3 to perform heating. Due to such heat exchange, the refrigerant becomes a liquid refrigerant having normal temperature under high pressure The liquid refrigerant is depressurized by the first pressure reducing device 4, and passes through the thermal storage bypass circuit 11. The refrigerant pathes through the outdoor heat exchanger 5 which has minimized the amount of heat exchange, and through the thermal storage releasing bypass circuit 8. Then the refrigerant is depressurized by the low pressure side pressure reducing device 9, and withdraws the stored heat from the thermal storage material 14 at the thermal storage releasing heat exchanger 10 to be evaporated and gasified. The refrigerant thus gasified returns to the compressor 1. At that time, the thermal storage material 14 is solidified by passing the stored heat to the refrigerant. This arrangement aims at offering a heating effect in a rapid and sufficient manner in the heat kickoff operation even if an outdoor temperature is low.
As the conventional air conditioning system is constructed as stated above, in the heating and thermal storage operation there is no difference between the refrigerant pressure in the thermal storage heat exchanger 6 and that in the outdoor heat exchanger 5, resulting in a decrease in refrigerant temperature at the inlet of the thermal storage heat exchanger 6. This creates problems in that the amount of thermal storage can not be obtained in a sufficient manner, and that although the thermal storage material 14 must have a melting point of 0.degree. C. or above for use as defrosting heat source, the presence of a low outdoor temperature makes defrosting impossible because the refrigerant temperature at the inlet of the thermal storage heat exchanger 6 lowers depending on a decrease in the outdoor air temperature. In addition, the arrangement wherein the low pressure side pressure reducing device 9 is arranged between the heat exchanger 5 and the thermal storage releasing heat exchanger 10 causes the refrigerant in the outdoor heat exchanger 5 to have medium pressure and medium temperature in the heating and defrosting operation and the heating kickoff operation, creating a problem in that in the heating and defrosting operation and in the heating kickoff operation a loss due to heat rejection from the outdoor heat exchanger 5 to the outdoor air is increased to lower operating efficiency.
Referring now to FIG. 12, there is shown a conventional heat pump system which has been disclosed in e.g. Japanese Unexamined Patent Publication No. 135753/1988. The system is constructed to have a thermal storage device in a refrigerant citcuit, allowing high heating capacity to be obtained at the kickoff of heating by use of the heat stored in the thermal storage device at night.
In FIG. 12, reference numeral 101 designates a compressor. Reference numeral 102 designates a four way reversing valve. To the four way reversing valve 102 are connected an outdoor heat exchanger 103, an expansion valve 104 as an expansion device, a thermal storage device 105 and an indoor heat exchanger 106 in series. These members constitute a basic heat pump refrigerant citcuit. Between the thermal storage device 105 and the indoor heat exchanger 106 are arranged a first solenoid valve 107 and an expansion valve 108 for kickoff heating in a parallel combination. There are provided a first bypass circuit 109 and a second bypass circuit 110 for bypassing the expansion valve 104, the first bypass circuit 109 having a second solenoid valve 111 and a check valve 112 therein, and the second bypass circuit 110 having a third solenoid valve 113 and a check valve 114 therein.
In the heat pump system having such a structure, when the heat stored in the thermal storage device 105 is utilized to carry out a heating kickoff operation, the operation is made as shown in FIG. 13. Specifically, the first solenoid valve 107 is closed, the second solenoid valve 111 is opened, and only a fan (not shown) for the indoor heat exchanger 106 is driven. The indoor heat exchanger 106 works as condenser, and the thermal storage device 105 functions as evaporator to withdraw the heat stored in the thermal storage device 105. Although the continuation of such operation lowers the temperature in the thermal storage device 105, high heating capacity can be obtained by absorbing heat from outdoor air as long as the evaporating temperature is higher than the temperature of the outdoor air.
When the temperature in the thermal storage device 105 lowers to prevent high heating capacity from being obtained, a heating and thermal storage operation starts in the way shown in FIG. 14. This operation is a cycle for storing heat to use in defrosting. In this cycle, the fan for the indoor heat exchanger 106 and a fan (not shown) for the outdoor heat exchanger 103 are driven, and the indoor heat exchanger 106 and the thermal storage device 105 work as condensers, carrying out heating and thermal storage simultaneously.
As the conventional heat pump system has such a structure, when a thermal storage operation has not been made for a long period during no heating operation, the temperature in the thermal storage device lowers, causing a thermal storage material to be solidified. This creates a problem in that when the heating and thermal storage operation starts from such state, it takes much time to increase a diffused air temperature at the time of the heating kickoff operation.
It is an object of the present invention to eliminate these problems, and to provide an air conditioning system capable of using stored heat to carry out a heating and defrosting operation and a heating kickoff operation in a highly effective manner in a way to prevent an outdoor air temperature from having adverse effect on defrosting effectiveness.
It is another object of the present invention to provide an air conditioning system capable of utilizing heat stored in a thermal storage device to blow off conditioned hot air at once at the time of a heating kickoff operation.
According to a first aspect of the present invention, there is provided an air conditioning system comprising a refrigerant circuit which is constituted by connecting a compressor, a four way reversing valve, an indoor heat exchanger, a first pressure reducing device and an outdoor heat exchanger in that order; a thermal storage heat exchanger which is arranged between the first pressure reducing device and the outdoor heat exchanger, and which forms a thermal storage device together with a thermal storage material; a second pressure reducing device arranged between the thermal storage heat exchanger and the outdoor heat exchanger; a thermal storage bypass circuit for bypassing the first pressure reducing device, the thermal storage heat exchanger and the second pressure reducing device, and having a third pressure reducing device and a two way medium pressure side valve therein; a three way valve arranged between the outdoor heat exchanger and the four way reversing valve; and a thermal storage releasing bypass circuit arranged between the three way valve and the compressor to bypass the four way reversing valve, and having a thermal storage releasing heat exchanger, which forms the thermal storage device; wherein at the time of a heating and thermal storage operation a refrigerant is circulated through the compressor, the four way reversing valve, the indoor heat exchanger, the first pressure reducing device, the thermal storage heat exchanger, the second pressure reducing device, the outdoor heat exchanger, the three way valve, the four way reversing valve and the compressor in that order; and wherein at the time of a heating kickoff operation or a heating and defrosting operation the refrigerant is circulated through the compressor, the four way reversing valve, the indoor heat exchanger, the thermal storage bypass circuit, the outdoor heat exchanger, the three way valve, the thermal storage releasing bypass circuit and the compressor in that order.
According to a second aspect of the present invention, there is provided an air conditioning system comprising a refrigerant circuit which is constituted by connecting a compressor, a four way reversing valve, an indoor heat exchanger, a first pressure reducing device and an outdoor heat exchanger in that order; a thermal storage heat exchanger which is arranged between the first pressure reducing device and the outdoor heat exchanger, and which forms a thermal storage device together with a thermal storage material; a second pressure reducing device arranged between the thermal storage heat exchanger and the outdoor heat exchanger; a thermal storage bypass circuit for bypassing the first pressure reducing device and the thermal storage heat exchanger, and having a two way medium pressure side valve therein; a three way valve arranged between the outdoor heat exchanger and the four way reversing valve; and a thermal storage releasing bypass circuit arranged between the three way valve and the compressor to bypass the four way reversing valve, and having a thermal storage releasing heat exchanger, which forms the thermal storage device; wherein at the time of a heating and thermal storage operation a refrigerant is circulated through the compressor, the four way reversing valve, the indoor heat exchanger, the first pressure reducing device, the thermal storage heat exchanger, the second pressure reducing device, the outdoor heat exchanger, the three way valve, the four way reversing valve and the compressor in that order; and wherein at the time of a heating kickoff operation or a heating and defrosting operation the refrigerant is circulated through the compressor, the four way reversing valve, the indoor heat exchanger, the thermal storage bypass circuit, the second pressure reducing device, the outdoor heat exchanger, the three way valve, the thermal storage releasing bypass circuit and the compressor in that order.
According to a third aspect of the present invention, there is provided air conditioning system comprising a refrigerant circuit which is constituted by connecting a compressor, a four way reversing valve, an indoor heat exchanger, a first pressure reducing device and an outdoor heat exchanger in that order; a thermal storage heat exchanger which is arranged between the first pressure reducing device and the outdoor heat exchanger, and which forms a thermal storage device together with a thermal storage material; a second pressure reducing device arranged between the thermal storage heat exchanger and the outdoor heat exchanger; a thermal storage bypass circuit for bypassing the first pressure reducing device, and having a two way medium pressure side valve therein; a three way valve arranged between the outdoor heat exchanger and the four way reversing valve; and a thermal storage releasing bypass circuit arranged between the three way valve and the compressor to bypass the four way reversing valve, and having a thermal storage releasing heat exchanger, which forms the thermal storage device; wherein at the time of a heating and thermal storage operation a refrigerant is circulated through the compressor, the four way reversing valve, the indoor heat exchanger, the first pressure reducing device, the thermal storage heat exchanger, the second pressure reducing device, the outdoor heat exchanger, the three way valve, the four way reversing valve and the compressor in that order; and wherein at the time of a heating kickoff operation or a heating and defrosting operation the refrigerant is circulated through the compressor, the four way reversing valve, the indoor heat exchanger, the thermal storage bypass circuit, the thermal storage heat exchanger, the second pressure reducing device, the outdoor heat exchanger, the three way valve, the thermal storage releasing bypass circuit and the compressor in that order.
According to a fourth aspect of the present invention, there is provided an air conditioning system comprising a refrigerant circuit; a thermal storage device which is arranged in the refrigerant circuit, and which can store heat and utilize the stored heat to increase heating capacity at the time of kickoff of heating; temperature detecting means for detecting a temperature at a thermal storage portion of a thermal storage and radiating heat exchanger which is housed in the thermal storage device; means for counting a thermal storage operation period required for the temperature detected at the thermal storage portion to achieve a predetermined value, for outputting a signal indicative of stopping a thermal storage operation when the detected temperature has achieved the predetermined value, for counting the lapse of a predetermined thermal storage operation stoppage period after stop of the thermal storage operation, and for outputting a signal indicative of starting the thermal storage operation when the predetermined thermal storage operation stoppage time has passed; and control means for comparing the counted thermal storage operation period with a preset value, and determining the next thermal storage operation stoppage period, depending on the length of the counted thermal storage operation period.
In the fourth aspect, it is preferable that the temperature detected at the thermal storage portion is a pipe temperature at a thermal storage side of the thermal storage and radiating heat exchanger.
In the fourth aspect, the preset value can be changed, depending on an operating condition. In the fourth aspect, the operating condition may be an outdoor air temperature. In the fourth aspect, the operating condition may be a driving condition of the compressor.